Known are thermoplastic polyurethane (TPU)-based halogen-free flame retardant compositions. TPU provides mechanical properties, low heat deformation, and flexibility suitable for many applications. TPU, however, carries several disadvantages. TPU is expensive and it also has a high material density. Furthermore, TPU-based halogen-free flame retardants shrink, particularly when injection molded.
Composites of TPU with conventional polyolefin fail to overcome these disadvantages of TPU. Compatibility between TPU and conventional polyolefin is poor due to the polarity difference between the components. Addition of conventional polyolefin to TPU typically decreases the flame retardant performance of the final composite. Moreover, TPU/polyolefin composites suffer from a dramatic drop in heat deformation properties compared to TPU alone. Polyolefin elastomers, such as ethylene-based elastomers, typically have a melting temperature below 100° C.
A need exists for a halogen-free TPU-based composition that maintains the superior mechanical properties and heat deformation performance of TPU, while not compromising the flame retardant performance. A need further exists for a TPU-based halogen-free flame retardant composition that does not shrink when injection molded.